Effects of ozonation and Alum coagulation on urban wastewater treatment excessive sludge quality improvement

Sludge excess treatment and disposal is a problem for most wastewater treatment plants in the world, considering the economic, environmental, social, and legal aspects. The amount produced by the sludge in the wastewater plants should be reduced to the possible extent to reduce the excessive costs of investment and management of a wastewater treatment plant. Furthermore, it is also necessary to minimize the turbidity of the supernatant left over from the process to a possible extent so that it may be used for irrigation and other recreational purposes. To achieve this purpose, thickening and dewatering of sludge methods are used. Since the conditioned sludge readily forms condensable and dehydrated products, sludge preparation operations are necessary in sewage treatment plants. The present study deals with the effect of ozone and alum on the quality improvement of excess sludge from the Shiraz sewage treatment plant. In this regard, an experiment was conducted in which alum acted as a coagulant and ozone as an oxidizer in excess sludge, both individually and concurrently. For that, a pilot model was used in the form of a glass cube of size ۳ liters and measured the parameters like SS, TSS of sludge, and supernatant's turbidity. The variable parameters were optimized first, like pH and dosage for ozone and alum. By the achieved optimum parameters, the sludge sedimentation improved by ۳۴.۳%, and Total suspended solids increased by ۲۲.۷% through the use of Ozone injection. Sludge sedimentation improved by ۳۱.۳% and ۲۹.۳%, while the total suspended solids increased by ۳۲.۲% and by ۳۱.۵% with alum addition under optimum parameters. The combined process of ozone injection and adding alum had a maximum ۴۳.۴% reduction in sludge volume.

کلیدواژه ها:

Ozonation ، coagulation ، Alum ، Sludge improvement ، wastewater